/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright 1997-2007 Sun Microsystems, Inc.  Portions Copyrighted 2008 Richard Schilling.
 *
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License. You can obtain
 * a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
 * or glassfish/bootstrap/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
 *
 * When distributing the software, include this License Header Notice in each
 * file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
 * Sun designates this particular file as subject to the "Classpath" exception
 * as provided by Sun in the GPL Version 2 section of the License file that
 * accompanied this code.  If applicable, add the following below the License
 * Header, with the fields enclosed by brackets [] replaced by your own
 * identifying information: "Portions Copyrighted [year]
 * [name of copyright owner]"
 *
 * Contributor(s): Richard Schilling (coderroadie@gmail.com)
 *
 * If you wish your version of this file to be governed by only the CDDL or
 * only the GPL Version 2, indicate your decision by adding "[Contributor]
 * elects to include this software in this distribution under the [CDDL or GPL
 * Version 2] license."  If you don't indicate a single choice of license, a
 * recipient has the option to distribute your version of this file under
 * either the CDDL, the GPL Version 2 or to extend the choice of license to
 * its licensees as provided above.  However, if you add GPL Version 2 code
 * and therefore, elected the GPL Version 2 license, then the option applies
 * only if the new code is made subject to such option by the copyright
 * holder.
 */

package javax.mail;

import java.io.*;
import java.util.Vector;
import javax.mail.event.MailEvent;

/**
 * Package private class used by Store & Folder to dispatch events.
 * This class implements an event queue, and a dispatcher thread that
 * dequeues and dispatches events from the queue.
 * Pieces stolen from sun.misc.Queue.
 * 
 * @author Bill Shannon
 */
class EventQueue implements Runnable {

    static class QueueElement {

        QueueElement next = null;
        QueueElement prev = null;
        MailEvent event = null;
        Vector vector = null;

        QueueElement(MailEvent event, Vector vector) {
            this.event = event;
            this.vector = vector;
        }
    }

    private QueueElement head = null;
    private QueueElement tail = null;
    private Thread qThread;

    public EventQueue() {
        qThread = new Thread(this, "JavaMail-EventQueue");
        qThread.setDaemon(true);  // not a user thread
        qThread.start();
    }

    /**
     * Enqueue an event.
     */
    public synchronized void enqueue(MailEvent event, Vector vector) {
        QueueElement newElt = new QueueElement(event, vector);

        if (head == null) {
            head = newElt;
            tail = newElt;
        } else {
            newElt.next = head;
            head.prev = newElt;
            head = newElt;
        }
        notifyAll();
    }

    /**
     * Dequeue the oldest object on the queue.
     * Used only by the run() method.
     * 
     * @return the oldest object on the queue.
     * @exception java.lang.InterruptedException if another thread has
     *                interrupted this thread.
     */
    private synchronized QueueElement dequeue() throws InterruptedException {
        while (tail == null)
            wait();
        QueueElement elt = tail;
        tail = elt.prev;
        if (tail == null) {
            head = null;
        } else {
            tail.next = null;
        }
        elt.prev = elt.next = null;
        return elt;
    }

    /**
     * Pull events off the queue and dispatch them.
     */
    public void run() {
        QueueElement qe;

        try {
            loop: while ((qe = dequeue()) != null) {
                MailEvent e = qe.event;
                Vector v = qe.vector;

                for (int i = 0; i < v.size(); i++)
                    try {
                        e.dispatch(v.elementAt(i));
                    } catch (Throwable t) {
                        if (t instanceof InterruptedException)
                            break loop;
                        // ignore anything else thrown by the listener
                    }

                qe = null;
                e = null;
                v = null;
            }
        } catch (InterruptedException e) {
            // just die
        }
    }

    /**
     * Stop the dispatcher so we can be destroyed.
     */
    void stop() {
        if (qThread != null) {
            qThread.interrupt();	// kill our thread
            qThread = null;
        }
    }
}
